1. Field of the Invention
The invention relates to a peptide and homologues thereof which inhibit the activity of TGF-xcex2 family growth factors in vertebrates, as well as TGF-xcex2-like growth factors in Drosophilia. Specifically, the invention relates to a highly potent fragment of the product of the Drosophilia short gastrulation gene (Sog).
2. History of the Related Art
During vertebrate development, growth factors in the TGF-xcex2 superfamily control a number of events in tissue differentiation and morphogenesis. Included in the TGF-xcex2 superfamily are the bone morphogenic proteins, which promote the growth of new bone tissue and differentiation of osteoblasts. Examples of members of this family of BMPs are BMP-4 and BMP-7, which suppress neurogenesis during early embroynic development and are active in aspects of adult physiology.
BMP-4 has been highly conserved through evolution and has a functional and structural homologue in Drosophilia, known as Dpp. BMP-4 can substitute for Dpp in Drosophilia (Padgett, et al., Proc. Natl.Acad.Sci. USA 90:2905-2909 (1993)) and Dpp is active in vertebrate tissues (Sampath, et al., Proc. Nat.Acad.Sci. USA, 90:6004-6008 (1993)). In vertebrates, chordin is a high affinity BMP-4 binding protein which inhibits BMP-4 and BMP-7 activity (Sasai, et al., Cell, 779-790 (1994)), in flies, the short gastrulation (Sog) protein inhibits Dpp activity (Francois, et al., Genes and Dev., 8:2602-2616 (1994)). Again, chordin and Sog are functional and structural homologues (Schmidt, et al., Development, 121:4319-4328 (1995) and Francois, et al., Cell, 80:19-20 (1995)). In particular, Sog inhibits BMP-4 activity in vertebrates in a manner similar to chordin (Schmidt, et al., id.), It is highly probable that Sog inhibits the activity of other members of the TGF-xcex2 family such as BMP-7, which is also inhibited by chordin.
Abnormal activity on the part of BMP-4 has been linked to human cancer, including osteosarcoma and certain leukemias. Interestingly, over-expression of BMP-4 (which is potentiated by BMP-7) has also been shown to stimulate the onset of alopecia (male pattern baldness) in mice, perhaps due to an effect on hair follicle development. Control of such activity can have therapeutic benefit in these and other conditions related to abnormalities in the functioning of TGF-xcex2 family growth factors, especially on the part of BMP-4.
The invention provides a highly potent inhibitor of TGF-xcex2 growth factor activity, with particular impact on BMP-4. In particular, the invention identifies a fragment of the Drosophilia Sog protein which has an unexpectedly high level of Dpp inhibitory activity as compared to the intact, wild-type protein.
Based on the known homologies between Dpp and BMP-4, as well as between Sog and chordin, together with other supportive data discussed below, it is predictable that the Sog fragment of the invention (hereafter, xe2x80x9cSuper-Sogxe2x80x9d) functions as an inhibitor of BMP-4 and BMP-7 activity in vertebrates. Surprisingly, Super-Sog has a broader scope of activity than wild-type Sog in the sense that mutant phenotypes not produced by Sog inhibition of Dpp are produced in response to Super-Sog. This phenomenon suggests that Super-Sog is more potent than Sog and/or that it affects additional receptor-ligand interactions not affected by the wild-type protein, such as those mediated by activin, a vertebrate endocrine regulator whose Drosophilia homologue mediates wing development.
The invention therefore provides Super-Sog (SEQ ID NO:1; amino acids 1-292 of Sog) and active variants thereof. Such variants include SEQ ID NO: 3, a recombinant Super-Sog peptide which includes 33 amino acids encoded by the pUAS expression vector; SEQ ID NO: 6, a Super-Sog peptide which includes a mutation (W-A) in the CR-1 sequence; and SEQ ID NO: 7, a Super-Sog peptide which terminates 5xe2x80x2 of the CR-1 sequence. Such variants also include Super-Sog with 5xe2x80x2 modifications, such as modifications to the Tolloid protease cleavage site, addition of other peptides and inclusion of additional 5xe2x80x2 regions of Sog (e.g., CR-2).
The invention further provides pharmaceutical compositions of Super-Sog and methods for their use. Especially, useful among the pharmaceutical compositions are those which are prepared so as to increase the bioavailability of Super-Sog in vivo by, for example, protecting the peptide against unintended proteolysis.
Methods for use of Super-Sog include its therapeutic use in arresting the development of mate pattern baldness, assisting in the treatment of cancer (e.g., osteosarcomas) and inhibiting TGF-xcex2 growth factor (e.g., BMP-4, BMP-7 and activin) mediated suppression of neurogenesis to, for example, enhance the viability of fetal nervous tissue grafts in the treatment of neurodegenerative disorders such as Alzheimer""s Disease, Parkinson""s Disease and Huntington""s Disease.